Method for regeneration of diesel soot filtering device

ABSTRACT

A method for regeneration of a diesel soot-filtering device includes the steps of inputting a flow resistance value that varies depending upon the amount of soot accumulated in the soot-filtering device; calculating the accumulated mileage and the flow resistance value (K); primarily compulsorily regenerating the diesel soot-filtering device if the mileage falls within a range from 200 to 10,000 km; and secondarily compulsorily regenerating the diesel soot-filtering device if the flow resistance value (K) falls within a range from 0.001 to 0.07.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on, and claims priority from Korean Application No. 10-2004-0039431, filed on Jun. 1, 2004, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for regeneration of a diesel soot-filtering device, and more particularly to such a device employing regeneration logic that considers both natural regeneration and compulsory regeneration of the device achieved by analyzing the degree of accumulated soot.

2. Background of the Related Art

In the development of a diesel soot-filtering device, an important aspect of the control logic is the determination regarding the continue use of the soot filtering device. For this purpose, the soot accumulated within the diesel soot-filtering device should be continuously burned so as to prevent the diesel soot-filtering device from being blocked. Accordingly, it is required that the temperature of the diesel soot-filtering device should be continuously increased. To this end, post-injection of fuel may be employed.

General conditions for the regeneration logic can be defined as follows: engine speed of about 1000 to 4000 rpm; total mileage of about 200 km; engine load of approximately 0.7 bar; vehicle speed of about 50 kph, and temperature of cooling water above about 50° C.

Under such conditions, the regeneration of the diesel soot-filtering device is theoretically accomplished. However, the above-mentioned conditions are merely a regeneration condition for random experimentation, and do not take into consideration the operating conditions and variances arising from mass production of a vehicle.

The above condition generally cannot be applied to a specific diesel vehicle because such regeneration is only for prevention of error, but not as a result of identification of the start point and the conditions of regeneration. Consequently, the regeneration logic according to the above-mentioned regeneration conditions never suggests a method of interrupting a decrease in fuel consumption ratio and an uncontrolled burning, which adversely affect the quality of the vehicle.

Currently, in order to manufacture and sell a diesel motor vehicle, it must be subjected to a number of durability tests and evaluation tests (e.g., European Evaluation Mode: EC mode, US Evaluation Mode: FTP-75 mode). Further, it is required that various development logics conform to given conditions and situations on a real roadway, including basic logic, error logic, soot compulsory regeneration logic, so as to prevent an unexpected trouble.

Sufficient data is needed for test variables in all the cases as described above. However, although sufficient test data is retained, the accurate amount and the accumulated extent of soot must be checked in order to usefully utilize such data. In order for a diesel motor vehicle to be equipped with a diesel soot-filtering device, engine data and vehicle data must be secured, and a sufficient time period for mapping such data is required.

How the captured soot is effectively burned to continuously reuse the soot-filtering device is one factor for the mounting of the device. The minimum and the highest-priority test variables to be previously taken into consideration in order to develop and equip the diesel soot-filtering device are as follows:

-   -   (1) Whether the temperature of exhaust gas is risen up due to         the post-injection of fuel (including Advance/Retard)     -   (2) Soot compulsory regeneration strategy according to engine         condition     -   (3) Checking both the loaded amount of soot and the start and         end points of soot compulsory regeneration     -   (4) Technology for preventing uncontrolled burning, etc.

As mentioned above, in order to manufacture and sell a diesel motor vehicle, it must be subjected to durability tests and evaluation tests. In doing so, sufficient data is needed for test variables in all the cases as described above.

After addressing the problems associated with item (1) of the above test variables, mapping and test data must be sufficiently retained. But in case of the item (3), although sufficient test data is retained, an accurate amount and accumulated extent of soot must be checked in order to usefully utilize such data. To this end, currently, an amount of soot accumulated actually present in a real vehicle and engine must be measured using a scale without other separate methods. Consequently, during the test of the real vehicle and engine, in order to check the start point of soot compulsory regeneration, it is required that the amount (unit: g) of soot currently accumulated within the soot-filtering device be measured using a scale after removing a corresponding soot-filtering device, followed by re-mounting so as to proceed with the test.

However, it is nearly impossible to carry out such a process since the weight of the soot-filtering device generally reaches 12 to 15 kg, and the soot weighs approximately 1 to 12 g which is in a relatively very small amount as compared to the weight of the device, resulting in a significant decrease in accuracy. In addition, since the weight of the soot varies even in the case where foreign substances adhere to the outer appearance of the soot-filtering device while traveling, it is impossible to accurately measure the weight of the soot in real time.

This is also applied to an engine test. The engine test undergoes much easier process than that in the vehicle test. Similarly, in this case, the amount of soot currently accumulated within the soot-filtering device must be measured using a scale after removing the soot-filtering device, which is the same as in the vehicle test. That is, the weight of a corresponding soot-filtering device is measured using a scale after it is removed, and then the device is re-mounted so as to proceed with the test.

Resultantly, in the case where such a test is repeatedly performed, the development period will be greatly extended as well as reliability of data measured will be significantly degraded.

Accordingly, first of all, it is necessary to set a random constant value which allows the amount of soot accumulated in a vehicle to be identified in real time. If this constant value is not set, it is difficult to grasp the accumulated amount of the soot. Such a constant value can be defined as a flow resistance, i.e., K factor. The constant value is a uniform constant value, which is not varied depending upon the condition of an engine, and varies depending upon the property of a diesel soot-filtering device.

A disadvantage of the conventional prior art resides in the fact that since the accurate amount of soot accumulated in the diesel soot-filtering device is not determined, the accurate start point of regeneration of the accumulated soot within the diesel soot-filtering device is also not established. As a result, the start point and the end point of regeneration of soot in the diesel soot-filtering device cannot be found, and there is little information regarding how much regeneration has been carried out. Moreover, it is not possible to develop data on how the degree of regeneration is to be achieved.

In consequence, in order to completely develop the diesel soot-filtering device, it is necessary to define data from the vehicle and engine test in real time, including data indicating the weight or mass of loaded soot. However, it is generally not possible to recognize presently loaded data regarding the soot. The reason for this is as follows: rpm of engine varying momentarily; momentarily varying pressure at front and rear ends of the soot-filtering device; amount of air and fuel varying every moment; and unmeasured amount of soot accumulated.

Although logic for the compulsory regeneration may be well designed, an uncontrolled burning may occur in a state where the logic is not used even once. Also, during the compulsory regeneration, much burden may be imposed on the diesel soot-filtering device. Therefore, there is a need for properly combining the compulsory regeneration logic of the previously filed patent and the natural regeneration logic according to CPF catalyst coating

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method for regeneration of a diesel soot-filtering device, in which an appropriate regeneration logic is implemented by combining a degree of a natural regeneration and a degree of derived K value on a basis of the fact that it is difficult to protect CPF, i.e., a diesel soot-filtering device with only compulsory regeneration logic in consideration of a natural regeneration condition prior to the detection of a flow resistance value, i.e., a constant value K, thereby achieving a complete regeneration of the diesel soot-filtering device.

According to one embodiment of the present invention, a method for regeneration of a diesel soot-filtering device includes the steps of: inputting a flow resistance value (i.e., a value obtained by dividing a difference between pressures at front and rear ends of the diesel soot-filtering device by the flow rate of exhaust gas) varying depending upon the amount of soot accumulated in the soot-filtering device regardless of the condition of an engine and a vehicle, an accumulated mileage of the vehicle, and a total volume of the exhaust gas to an ECU; calculating the accumulated mileage and the flow resistance value (K) by the ECU; primarily compulsorily regenerating the diesel soot-filtering device if the mileage falls within a range from 200 to 10,000 km; and secondarily compulsorily regenerating the diesel soot-filtering device if the flow resistance value (K) falls within a range from 0.001 to 0.07.

In another embodiment, the method may further include primarily compulsorily regenerating the diesel soot-filtering device if the mileage is more than 1,000 km; and secondarily compulsorily regenerating the diesel soot-filtering device if the flow resistance value (K) is more than 0.003.

In a further embodiment, the primary compulsory regeneration of the diesel soot-filtering device may be performed in a condition where only some of soot can be burnt at an intermediate temperature of from 550° C. to 600° C. Thereafter, the secondary compulsory regeneration of the diesel soot-filtering device may be performed at a high temperature of 600° C. to 650° C.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart illustrating a method for regeneration of a diesel soot-filtering device according to the present invention;

FIG. 2 is a graph illustrating a variation in a K value according to the accumulation of mileage; and

FIG. 3 is a graph illustrating the distribution of the temperature at a CPF inlet of a diesel passenger vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiment of the present invention with reference to the attached drawings.

In view of the above-mentioned conditions, there is needed an improved method for determining the start and end points for the regeneration of a soot filtering device. Start and end points for regeneration may be determined by measuring a flow resistance value obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas depending upon the amount of soot accumulated in a soot-filtering device regardless of the conditions of the engine and vehicle. This permits determination of a degree of accumulated soot and the measured corresponding flow resistance value, so that a software basis may be prepared. The start and end points of compulsory regeneration of the soot-filtering device can be easily determined through the later measurement of a flow resistance value in a real vehicle.

More specifically, and with reference to FIGS. 1 and 2, a method for determining regeneration start and end points may include steps of: measuring a flow resistance value (i.e., a value obtained by dividing a difference between pressures at front and rear ends of a diesel soot-filtering device by the flow rate of exhaust gas) varying depending upon the amount (SL) of soot accumulated in the soot-filtering device regardless of the condition of an engine and a vehicle; previously storing the amount (SL) of accumulated soot and the measured corresponding flow resistance value (FR1) in a storage/computation means to datalize the stored amount of the soot; setting the flow resistance value (FR1) corresponding to the previously stored amount of soot as a reference of the start point of a compulsory regeneration of the soot-filtering device; measuring a flow resistance value (FR2) in a real vehicle, and at the same time, computing and identifying the amount (SL) of soot corresponding to the measured flow resistance value (FR2) through the storage/computation means; and comparing/computing the flow resistance value (FR2) in the real vehicle and the corresponding flow resistance value (FR1) of the identified amount (SL) of soot through the storage/computation means, whereby the start and end points of a compulsory regeneration of the soot-filtering device are determined, and simultaneously whether the soot-filtering device is compulsorily regenerated is determined.

In addition, the storage/computation means compares the flow resistance value (FR2) measured in a real vehicle with the previously stored corresponding flow resistance value (FR1). When the measured flow resistance value (FR2) is identical to the previously stored corresponding flow resistance value (FR1), said means determines that a current regeneration start point is the start point of the compulsory regeneration while compulsorily regenerating the soot-filtering device. The storage/computation means may comprise an electronic control unit (ECU) including a processor, memory and associated hardware and software as may be selected and programmed by a person of ordinary skill in the art based on the teachings contained herein.

Using the above method, more details of which are set forth in Korean Application No. 2004-31211, filed May 4, 2004, which is incorporated herein by reference, a basis for determining the start and end points of a regeneration of the soot-filtering device is provided. When the start and the end of the compulsory regeneration are determined and the soot-filtering device is regenerated, there is generally no problem with regeneration. Nevertheless, in some circumstances, there may be some uncertainty as to when the start and end points of the compulsory regeneration will be detected.

It can be seen from FIG. 3 that as a result of temperature measurement in a diesel passenger vehicle, the inlet temperature of the diesel soot-filtering device ranges from 300 to 350°. Such a temperature range meets a condition where auto-ignition of a catalyst coated on a DPF carrier within the diesel soot-filtering device can occur sufficiently. That is, auto-ignition of soot is progressed on CPF, so that a total amount of soot discharged from an engine is not accumulated. Resultantly, when a driver is in a traveling state on a high temperature area such as an express highway, a K value is decreased steeply and a condition where a regeneration mode cannot be transferred to a compulsory regeneration mode is continuously kept, which is shown in FIG. 2.

Referring to FIG. 2, when a K value exceeds 0.03 the regeneration mode is transferred to a compulsory regeneration mode. At this time, the compulsory regeneration mode of a vehicle is not actuated when a mileage is less than 10,000 km. Here, it may be doubtful that a vehicle must be continued to travel irrespective of the absence of the compulsory regeneration mode in case of a mileage of 10,000 km or less.

It is encouraging that a vehicle can travel over 10,000 km without its compulsory regeneration in terms of economical efficiency of the fuel consumption ratio of a vehicle, but it cannot be ensured that an uncontrolled burning would not occur during the traveling over 10,000 km.

Embodiments of the present invention thus may further take advantage of the fact that a flow resistance value, i.e., a K value varying depending upon the amount of soot accumulated in the soot-filtering device is measured to perform the compulsory regeneration of the soot-filtering device in such a fashion that the accumulated mileage of a vehicle is checked prior to the detection of the K value in consideration of a natural regeneration so as to perform a secondary compulsory regeneration of the soot-filtering device.

An explanation of a method for regeneration of a diesel soot-filtering device, with start and end points already determined, preferably as above, according to a further embodiment of the present invention will be made hereinafter.

At a first step, data for compulsory regeneration of the soot-filtering device is input to an engine electronic control unit (ECU), which also may be constituted as the ECU described above. The ECU may be combined with or provided separately from the above-mentioned ECU. That is, a flow resistance value K varying depending upon the amount of soot accumulated in the soot-filtering device regardless of the condition of an engine and a vehicle, an accumulated mileage of the vehicle, and a total volume of the exhaust gas are input to an ECU.

Subsequently, the accumulated mileage and the flow resistance value (K) which are input are calculated by the ECU. At this time, if the accumulated mileage falls within a range from 200 to 10,000 km, preferably more than 1,000 km, the diesel soot-filtering device is primarily regenerated compulsorily.

Such regeneration of the diesel soot-filtering device based on the mileage is carried out in a state where the flow resistance value K is not detected. This means that it is determined that the amount of soot accumulated in the diesel soot-filtering device is below a level which can be regenerated. As a result, the mileage of the vehicle must be independently detected by the kind of vehicle, which must be regarded as the time point when it is required to properly check and protect fuel consumption ratio and the soot-filtering device.

In this case, since the accumulated soot is in a small amount, although the compulsory regeneration of the soot-filtering device is performed at a high temperature of 600° C. to 650° C. or more than 650° C., an uncontrolled burning does not occur in the diesel soot-filtering device.

Next, the diesel soot-filtering device is secondarily regenerated compulsorily if the flow resistance value (K) falls within a range from 0.001 to 0.07, preferably more than 0.003.

At this time, the K value is a constant which is differently represented depending upon the conditions of a vehicle and an engine. The k value can be limited to a value ranging from 0.001 to 0.07. In case of the mileage, the mileage is limited to a value ranging from 200 to 10,000 km in view of the loaded amount of catalyst.

In the meantime, although it is determined that the mileage is less than 200 km in the range of the limited K value, the K value has been represented due to an increase in the detected amount of soot. Therefore, in the case where the compulsory regeneration logic is performed at a high temperature, the uncontrolled burning occurs in the soot-filtering device. Accordingly, as described above, when the K value falls within a range from 0.001 to 0.07, preferably more than 0.003, the diesel soot-filtering device is secondarily regenerated compulsorily. At this time, the compulsory regeneration of the diesel soot-filtering device is performed in a condition where only some of soot can be burnt at an intermediate temperature of from 550° C. to 600° C., and then the secondary compulsory regeneration of the diesel soot-filtering device is performed at a high temperature of 600° C. to 650° C. to thereby achieve a complete regeneration of the diesel soot-filtering device.

As described above, according to the method for regeneration of a diesel soot-filtering device present invention, an appropriate regeneration logic is implemented by combining a degree of a natural regeneration and a degree of derived K value in consideration of a natural regeneration condition prior to the detection of a flow resistance value, i.e., a constant value K so as to perform a secondary compulsory regeneration of the soot-filtering device, thereby achieving a complete regeneration of the diesel soot-filtering device.

Further, the inventive method can be employed as a software key for the compulsory regeneration of the diesel soot-filtering device, and can be utilized as a mapping element of an ECU.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. 

1. A method for regeneration of a diesel engine soot-filtering device for a vehicle comprising: inputting a flow resistance value that varies depending upon the amount of soot accumulated in the soot-filtering device regardless of a condition of the engine and the vehicle, an accumulated mileage of the vehicle, and a total volume of the exhaust gas to an ECU; calculating the accumulated mileage and the flow resistance value (K) by the ECU; primarily compulsorily regenerating the diesel soot-filtering device if the mileage falls within a range from 200 to 10,000 km; and secondarily compulsorily regenerating the diesel soot-filtering device if the flow resistance value (K) falls within a range from 0.001 to 0.07.
 2. The method according to claim 1, further comprising: primarily compulsorily regenerating the diesel soot-filtering device if the mileage is more than 1,000 km; and secondarily compulsorily regenerating the diesel soot-filtering device if the flow resistance value (K) is more than 0.003.
 3. The method according to claim 1, wherein the primary compulsory regeneration of the diesel soot-filtering device is performed in a condition where only some of soot can be burnt at an intermediate temperature of from 550° C. to 600° C., and then the secondary compulsory regeneration of the diesel soot-filtering device is performed at a high temperature of 600° C. to 650° C.
 4. The method according to claim 1, wherein the flow resistance value comprises a value obtained by dividing a difference between pressures at a front and a rear end of the diesel soot-filtering device by a flow rate of exhaust gas 